Liquid ejection head, liquid ejection device

ABSTRACT

A liquid ejection head including a piezoelectric element having a piezoelectric layer and electrodes The piezoelectric layer is 3 μm or less in thickness. The piezoelectric layer is made of a piezoelectric material including bismuth manganate ferrate and barium titanate. The piezoelectric layer is preferentially oriented with the (110) plane.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2010-045973 filed on Mar. 2, 2010 and Japanese Patent Application No.2011-014619 filed on Jan. 26, 2011. The entire disclosures of JapanesePatent Application Nos. 2010-045973 and 2011-014619 are herebyincorporated herein by reference.

BACKGROUND

1. Technical Field

The present invention relates to a liquid ejection head and a liquidejection device provided with piezoelectric elements having electrodesand a piezoelectric layer of a piezoelectric material, and adapted toexpel droplets of liquid from nozzle openings.

2. Related Art

One known structure for a piezoelectric element has a piezoelectriclayer of a piezoelectric material that exhibits an electrical-mechanicalconversion function, for example, a crystallized dielectric material,sandwiched by two electrodes. Piezoelectric elements of this kind may beinstalled in a liquid ejection head to serve as actuator devices thatoscillate in flexural oscillation mode, for example. One typical exampleof a liquid ejection head, for example, is an inkjet recording head thatincludes oscillator plates which partially define pressure generationchambers communicating with nozzle openings for expelling ink droplets,the head being adapted to pressurize the ink of the pressure generationchambers through deformation of the oscillator plates by piezoelectricelements in order to expel ink droplets from the nozzle openings. Thepiezoelectric elements installed in such an inkjet head are produced,for example, by forming a uniform piezoelectric material layer over theentire surface of the oscillator plate by deposition technique, andetching away the piezoelectric material layer by a lithography processinto shapes that correspond to the pressure generation chambers, to forman independent piezoelectric element for each of the pressure generationchambers.

An example of a piezoelectric material used in such piezoelectricelements is lead zirconate titanate (PZT) (see Japanese Laid-Open PatentApplication Publication No. 2001-223404).

SUMMARY

However, reduced lead levels in piezoelectric materials are increasinglydesirable due to environmental concerns. An example of a lead-freepiezoelectric material is BiFeO₃, which has a perovskite structurerepresented by ABO₃, for example. A problem with such BiFeO₃ basedpiezoelectric materials which contain Bi and Fe is that piezoelectriccharacteristics (strain rate) tend to be low owing to the relatively lowrelative dielectric constant. This problem is not limited to liquidejection heads typified by inkjet heads, and similar problems areencountered with piezoelectric elements of actuator devices installed inother types of devices as well.

With the foregoing in view, it is an object of the present invention toprovide a liquid ejection head, a liquid ejection device, and apiezoelectric element that are both environmentally friendly and afforda high relative dielectric constant.

A liquid ejection head according to a first aspect of the presentinvention includes a piezoelectric element having a piezoelectric layerand electrodes provided on the piezoelectric layer. The piezoelectriclayer is 3 μm or less in thickness. The piezoelectric layer is made of apiezoelectric material containing a perovskite compound includingbismuth manganate ferrate and barium titanate. The piezoelectric layeris preferentially oriented with the (110) plane.

According to this aspect, a liquid ejection head having a piezoelectriclayer with low lead content, that is, a reduced lead content, and a highrelative dielectric constant is obtained using a piezoelectric layerthat is 3 μm or less in thickness, is composed of a piezoelectricmaterial containing a perovskite compound including bismuth manganateferrate and barium titanate, and is preferentially oriented with the(110) plane.

The electrodes may include a platinum film oriented with the (111)plane, and the piezoelectric layer may be formed on the platinum film.Even if the electrodes have a platinum film oriented with the (111)plane, the liquid ejection head according to such a configuration willhave a piezoelectric layer that is oriented with the (110) plane, whilealso having a low lead content and a high relative dielectric constant.

The piezoelectric layer is preferably a spontaneously oriented film.Such a configuration makes it possible to provide a liquid ejection headhaving a piezoelectric layer obtained without having to orient thematerial under an applied magnetic field, provide the substrate of thepiezoelectric film with a layer for controlling orientation, or performanother similar operation.

The piezoelectric layer preferably further includes SiO₂. Such aconfiguration makes it possible to provide a liquid ejection head havingpiezoelectric elements with excellent insulating properties.

The piezoelectric layer preferably contains SiO₂ in an amount of 0.5 mol% or more and 5 mol % or less with respect to the perovskite compound.Such a configuration makes it possible to provide a liquid ejection headhaving a piezoelectric layer with dependably low lead content, highrelative dielectric constant, and excellent insulating properties.

A liquid ejection device according to another aspect of the presentinvention includes the liquid ejection head of the preceding aspect.According to this aspect, the liquid ejection device is provided with aliquid ejection head having a piezoelectric layer with low lead contentand a high relative dielectric constant, thereby affording a device withexcellent ejection characteristics and negligible environmental impact.

A piezoelectric element according to another aspect of the presentinvention includes a piezoelectric layer and an electrode provided onthe piezoelectric layer. The piezoelectric element is characterized inthat the piezoelectric layer is 3 μM or less in thickness. Thepiezoelectric layer is made of a piezoelectric material containing aperovskite compound including bismuth manganate ferrate and bariumtitanate. The piezoelectric layer is preferentially oriented with the(110) plane. According to this aspect, a piezoelectric element having apiezoelectric layer with low lead content and a high relative dielectricconstant is obtained using a piezoelectric layer that is 3 μm or less inthickness, is composed of a piezoelectric material containing aperovskite compound including bismuth manganate ferrate and bariumtitanate, and is preferentially oriented with the (110) plane.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of thisoriginal disclosure:

FIG. 1 is an exploded perspective view of a simplified configuration ofa recording head according to a first embodiment.

FIG. 2A is a plan view of the recording head, and FIG. 2B is a crosssectional view of the recording head according to the first embodiment.

FIG. 3 is a drawing depicting a P-V curve in a first embodiment.

FIG. 4 is a drawing depicting a P-V curve in a second embodiment.

FIG. 5 is a drawing depicting a P-V curve in a third embodiment.

FIG. 6 is a drawing depicting a P-V curve in a fourth embodiment.

FIG. 7 is a drawing depicting a P-V curve in a first comparativeexample.

FIG. 8 is a drawing depicting a P-V curve in a second comparativeexample.

FIG. 9 is a drawing depicting measurements of relative dielectricconstant.

FIG. 10 is a drawing showing an XRD pattern in the first embodiment.

FIG. 11 is a drawing showing an XRD pattern in the second embodiment.

FIG. 12 is a drawing showing an XRD pattern in the third embodiment.

FIG. 13 is a drawing showing an XRD pattern in the fourth embodiment.

FIG. 14 is a drawing showing an XRD pattern in the first comparativeexample.

FIG. 15 is a drawing showing an XRD pattern in the second comparativeexample.

FIG. 16 is a 2-dimensional sensed image in the first embodiment.

FIG. 17 is a drawing showing a simplified configuration of a recordingdevice according to an embodiment of the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS First Embodiment

FIG. 1 is an exploded perspective view showing a simplifiedconfiguration of an inkjet recording head as an example of a liquidejection head according to a first embodiment of the invention; and FIG.2A is a plan view and FIG. 2B is a cross sectional view thereof acrossA-A′.

As shown in FIGS. 1 and 2, in the present embodiment there is provided aflow-defining substrate 10 made of a single-crystal silicon substratewith a resilient film 50 of silicon dioxide formed on one face.

A plurality of pressure generation chambers 12 are arrayed along thewidth direction of the flow-defining substrate 10. A communicatingportion 13 is formed in a zone situated at the lengthwise outer ends ofthe pressure generation chambers 12 of the flow-defining substrate 10,and the communicating portion 13 communicates with the pressuregeneration chambers 12 via ink supply channels 14 and communicatingchannels 15 which are individually provided to the pressure generationchambers 12. The communicating portion 13 communicates with a reservoirportion 31 of a protective substrate, discussed later, and constitutespart of a reservoir which provides a common ink chamber for the pressuregeneration chambers 12. The ink supply channels 14 are narrower in widththan the pressure generation chambers 12, and serve to maintain a givenlevel of flow channel resistance of the ink inflowing to the pressuregeneration chambers 12 from the communicating portion 13. In the presentembodiment, the ink supply channels 14 are formed by constricting thewidth of the flow channels from one side; however, the ink supplychannels may also be formed by constricting the width of the flowchannels from both sides. Alternatively, the ink supply channels may beconstricted in the thickness direction rather than constricting thewidth of the flow channels. According to the present embodiment, theflow-defining substrate 10 is provided with liquid flow channels whichinclude the pressure generation chambers 12, the communicating portion13, the ink supply channels 14, and the communicating channels 15.

A nozzle plate 20 having nozzle openings 21 communicating at locationsin proximity to the ends on the opposite side from the ink supplychannels 14 in the pressure generation chambers 12 is affixed with anadhesive, thermal welding film, or other means, at the open face of theflow-defining substrate 10. The nozzle plate 20 may be made, forexample, of glass-ceramics, a single-crystal silicon substrate,stainless steel, or the like.

Meanwhile, to the opposite side from the open face in this flow-definingsubstrate 10, the resilient film 50 is formed in the above manner, andover this resilient film 50 there is disposed an intimate adhesion layer56 of titanium aluminum nitride (TiAlN) or the like intended to improveintimate adhesion of the resilient film 50 to the foundation of a firstelectrode 60. While TiAlN is used as the intimate adhesion layer 56 inthe present embodiment, the material of the intimate adhesion layer 56may differ depending on factors such as the type of first electrode 60and the foundation for it; oxides or nitrides containing titanium,zirconium, or aluminum, or SiO₂, MgO, CeO₂, or the like may be used.Optionally, an insulator film of zirconium oxide or the like may beformed between the resilient layer and the intimate adhesion layer 56.

The first electrode 60, a piezoelectric layer 70 which is a thin film 3μm or less, preferably between 0.3 and 1.5 μm, in thickness andpreferentially oriented with the (110) plane (for example, 60% or more),and a second electrode 80, are built up over the intimate adhesion layer56 to form a piezoelectric element 300. Here, the piezoelectric element300 refers to the section that includes the first electrode 60, thepiezoelectric layer 70, and the second electrode 80. Typically, eitherone of the electrodes of the piezoelectric element 300 is provided as acommon electrode, while the other electrode and the piezoelectric layer70 are patterned individually for each of the pressure generationchambers 12. In the present embodiment, the first electrode 60 isprovided as the common electrode for the piezoelectric elements 300,while the second electrode 80 is an individual electrode provided toeach of the piezoelectric elements 300; however, reversing thisarrangement due to driver circuit or wiring considerations poses noparticular difficulty. Here, the piezoelectric element 300 and theoscillator plate that gives rise to displacement driven by thepiezoelectric element 300 are together termed an actuator unit. In theexample described above, the resilient film 50, the intimate adhesionlayer 56, and the first electrode 60, and the optional insulator filmact as the oscillator plate; however, no limitation thereto is imposed,and the resilient film 50 and the intimate adhesion layer 56 need not beprovided, for example. Alternatively, the piezoelectric element 300 maysubstantially double as the oscillator plate.

In the present embodiment, the piezoelectric layer 70 is made from apiezoelectric material containing a perovskite compound that includesbismuth manganate ferrate and barium titanate. A perovskite compound isa compound having the perovskite structure. This perovskite structurespecifically produces an 8-faced body (octagon) of ABO₃ structure inwhich the A site has 12-fold oxygen coordination and the B site has6-fold oxygen coordination. Bi or Ba are situated at the A sites, whileFe, Mn, or Ti is situated at the B sites.

Where the piezoelectric layer 70 is 3 μm or less in thickness, is madeof a perovskite compound that includes bismuth manganate ferrate andbarium titanate, and is preferentially oriented with the (110) plane,the piezoelectric layer will be lead-free yet have a high relativedielectric constant, as shown in the embodiments discussed later.Consequently, the piezoelectric layer 70 will have good piezoelectriccharacteristics such that, for example, the oscillator plate experienceslarge displacement at small voltages.

In preferred practice the piezoelectric layer 70 further contains SiO₂.It is hypothesized that this SiO₂ does not substitute onto the A sitesor B sites in the perovskite compound, but rather is present as SiO₂ atgrain boundaries of the perovskite compound formed, for example, by thebismuth manganate ferrate and the barium titanate (e.g., (Bi, Ba) (Fe,Mn, Ti)O₃). By including SiO₂ in the piezoelectric layer 70, theresultant piezoelectric element 300 will be lead-free and will have ahigh relative dielectric constant and excellent insulating properties,as shown in the embodiments discussed later. It is hypothesized that thereason for the excellent insulating properties is that the presence ofSiO₂ at grain boundaries in the perovskite compound has the effect ofinhibiting leak paths.

The perovskite compound contained in the piezoelectric layer 70 maycontain other compounds having the perovskite structure, for example,BiZn_(1/2)Ti_(1/2)O₃, (Bi_(1/2)K_(1/2))TiO₃, (Bi_(1/2)Na_(1/2))TiO₃, or(Li, Na, K) (Ta, Nb)O₃.

No particular limitation is imposed as to the ratio of Fe and Mn of thebismuth manganate ferrate which is the principal component of theperovskite compound, and the level of Mn may be more than 1 mol % butless than 10 mol % of the total molar quantity of Fe and Mn. Nor is anyparticular limitation imposed as to the proportions of bismuth manganateferrate, barium titanate, or the optional SiO₂. For example, the levelof bismuth manganate ferrate is more than 60 mol %, and preferably atleast 70 mol % but not more than 80 mol %, with respect to theperovskite compound, more specifically to the total molar quantity ofbismuth manganate ferrate, barium titanate, etc. Consequently, theproportion of compounds having the perovskite structure such as bariumtitanate is less than 40 mol % in the perovskite compound. Such aperovskite compound composed, for example, of bismuth manganate ferrateand barium titanate is represented by Equation (1) below.

xBi(Fe_(1-a),Mn_(a))O₃-yBaTiO₃  (1)

(0.06<x<1, 0<y<0.40, and preferably 0.70≦x≦0.80, 0.20≦y≦0.30, x+y=1, and0.01<a<0.10.)

While no particular limitation is imposed as to the level of SiO₂ whereincluded in the piezoelectric layer 70, the piezoelectric layer 70 maybe made of piezoelectric material containing at least 0.5 mol % but nomore than 5 mol %, preferably at least 1.5 mol % but no more than 2.5mol %, with respect to the perovskite compound.

No particular limitation is imposed as to the method of forming suchpiezoelectric elements 300 on the flow-defining substrate 10, and theelements may be manufactured by the following method, for example.First, a silicon dioxide film of silicon dioxide (SiO₂) or the likeconstituting the resilient film 50 is formed on the surface of the waferthat used for the flow-defining substrate, which is a silicon wafer.Next, the intimate adhesion layer 56 of titanium aluminum nitride or thelike is formed over the resilient film 50 (silicon dioxide film).

Next, the first electrode 60 composed of platinum, iridium, iridiumoxide, or a stacked layer structure thereof is formed over the entireface of the intimate adhesion layer 56 by a sputtering process or thelike, and then patterned.

Next, the piezoelectric layer 70 is built up. No particular limitationis imposed as to the method of manufacture of the piezoelectric layer70, but the piezoelectric layer 70 may be formed, for example, using ametal-organic decomposition (MOD) method involving dissolving/dispersinga metal compound in a solvent then applying and drying the solution,followed by baking at high temperature to obtain a piezoelectric layer70 made of metal oxide. The method of manufacture of the piezoelectriclayer 70 is not limited to MOD, and other methods, for example, chemicalsolution methods such as the sol-gel method, laser ablation methods,sputtering methods, pulsed laser deposition (PLD) methods, CVD methods,aerosol deposition methods, and the like may be used as well.

For example, a sol or MOD solution (precursor solution) that contains adesired composition ratio of metal compounds, specifically, metalcompounds including Bi, Fe, Mn, Ba, and Ti, and that optionally containsadded SiO₂, is applied onto the first electrode 60 by a spin coatingmethod, etc., to form a piezoelectric precursor film (coating step).

The coated precursor solution is prepared by combining metal compoundsthat respectively include Bi, Fe, Mn, Ba, and Ti so as to give thedesired molar ratios of each metal, and dissolving or dispersing themixture into an organic solvent such as an alcohol. As metal compoundsrespectively including Bi, Fe, Mn, Ba, and Ti there may be employed, forexample, metal alkoxides, salts of organic acids, β diketone complexes,and the like. Examples of metal compounds containing Bi include bismuthbenzoate, bismuth oxyacetate, bismuth octylate, bismuth octanoate,bismuth citrate, bismuth acetate, tri-t-amyloxy bismuth, triethoxybismuth, tris(dipivaloylmethanate) bismuth, triphenyl bismuth, andtri-i-propoxide bismuth. Examples of metal compounds containing Feinclude iron octylate, iron octanoate, iron format, iron stearate,triethoxy iron, iron tris(acetylacetonate), tri-i-propoxy iron, and thelike. Examples of metal compounds containing Mn include manganeseoctylate, manganese octanoate, manganese acetate, manganeseacetylacetonate, and the like. Examples of metal compounds containing Bainclude barium benzoate, barium octanoate, barium octylate, bariumoleate, barium formate, barium citrate, barium acetate, barium oxalate,barium tartrate, diethoxy barium, di-i-butoxy barium, di-n-butoxybarium, di-sec-butoxy barium, di-t-butoxy barium, di-i-propoxy barium,di-n-propoxy barium, dimethoxy barium, barium hydroxide, bariumthiocyanate, barium naphthenate, barium lactate, bariumdipivaloylmethanate, barium di(methoxyethoxide),bis(acetylacetonate)diaqua barium, bis(dipivaloylmethanate) barium,barium propionate, and barium laurate. Examples of metal compoundscontaining Ti include titanium octylate, titanium octanoate, titaniumoleate, di(isopropoxy) bis(dipivaloylmethanate) titanium, tetraethoxytitanium, tetrakisdiethylamino titanium, tetrakis(dimethylamino)titanium, tetra-n-butoxy titanium, tetra-i-butoxy titanium,tetra-sec-butoxy titanium, tetra-t-butoxy titanium, tetra-i-propoxytitanium, tetra-n-propoxy titanium, tetramethoxy titanium, and the like.Solvents for the precursor solution include propanol, butanol, pentanol,hexanol, octanol, ethylene glycol, propylene glycol, octane, decane,cyclohexane, xylene, toluene, tetrahydrofuran, acetic acid, octylicacid, and the like.

In preferred practice, the precursor solution is one that includes ironoctylate. Where iron octylate is included, simply by forming apiezoelectric precursor film by coating or the like and bringing aboutcrystallization thereof by heating, a piezoelectric layer 70 that ispreferentially oriented with the (110) plane can be formed throughspontaneous orientation, that is, without an operation to orient thematerial under an applied magnetic field, or an operation involvingproviding the foundation of the piezoelectric layer 70 with a layer forcontrolling orientation, or the like. The precursor solution includingiron octylate may be a precursor solution containing added iron octylateper se as the iron source, or one in which a metal compound other thaniron octylate is used as the iron source, and a precursor solution forcoating purposes that contains iron octylate is obtained through ligandsubstitution by the solvent or the like. In case of a precursor solutionthat does not include iron octylate, for example, one including irontris(acetylacetonate) as described in the comparative examples discussedlater, coating of the precursor solution and bringing aboutcrystallization of the piezoelectric precursor film by heating does notbring about a piezoelectric layer 70 that is preferentially orientedwith the (110) plane.

In addition, adjusting the ligands of the elements by changing thesolvent or metal compounds or varying the ratio of the elemental Bi, Fe,Mn, Ba and Ti in the precursor solution makes it possible to adjust thedegree to which the (110) plane of the piezoelectric layer 70 isoriented.

Next, the piezoelectric precursor film is heated to prescribedtemperature and dried for a given duration (drying step). Next, thedried piezoelectric precursor film is heated to a prescribed temperatureand held for a given duration to bring about degreasing (degreasingstep). Here, degreasing refers to driving off organic componentscontained in the piezoelectric precursor film, for example, NO₂, CO₂,H₂O, and so on.

Next, the piezoelectric precursor film is heated to prescribedtemperature, for example between 600° C. and 700° C., and held for agiven duration to bring about crystallization and form the piezoelectricfilm (baking step). The heating unit used in the drying step, degreasingstep, and baking step may be a rapid thermal annealing (RTA) unitdesigned to heat by irradiation with a UV lamp, or a hot plate or otherdevice.

Optionally, the aforementioned coating step, drying step, and degreasingstep or the coating step, drying step, degreasing step, and baking stepmay be repeated multiple times depending on factors such as desired filmthickness, to form a piezoelectric layer composed of a multilayerpiezoelectric film.

After the piezoelectric layer 70 has been formed, the second electrode80 layer is formed from a metal such as platinum, for example, over thepiezoelectric layer 70; and the piezoelectric layer 70 and the secondelectrode 80 are then patterned simultaneously to form the piezoelectricelement 300.

Optionally, a subsequent post-anneal may be carried out at a temperaturerange of between 600° C. and 700° C. By so doing, a good interface canbe formed between the piezoelectric layer 70 on the one hand and thefirst electrode 60 and second electrode 80 on the other, and thecrystallinity of the piezoelectric layer 70 may be improved.

A more detailed description of the present invention is given belowbased on the preferred working examples. The invention is not limited tothe working examples hereinbelow.

First Working Example

First, an SiO₂ film having film thickness of 400 nm was formed bythermal oxidation of the surface of a silicon substrate. Next, using anRF sputtering method, a TiAlN film having film thickness of 100 nm wasformed over the SiO₂ film. Next, using a DC sputtering method, an Irfilm having film thickness of 100 nm and an IrO₂ film having filmthickness of 30 nm were formed successively over the TiAlN film, and aPt film oriented in the (111) plane was formed thereon by a vapordeposition method, to form the first electrode 60.

Next, a piezoelectric layer was formed on the first electrode by a spincoating method. The method is as follows. First, metal compounds of Bi,Fe, Mn, Ba, Ti, and Si, more specifically bismuth octylate, ironoctylate, manganese octylate, barium octylate, titanium octylate, andSiO₂, together with an octane solvent, are mixed in prescribedproportions to prepare a precursor solution. In the resultant solutionthe total number of moles of Bi, Fe, Mn, Ba, and Ti was 0.25 mol/L. Thisprecursor solution was dripped onto the substrate on which the TiAlNfilm and the first electrode were formed, and the substrate was thenspun at 1,500 rpm to form a piezoelectric precursor film (coating step).Next, drying/degreasing were carried out for 3 minutes at 350° C.(drying and degreasing step). After repeating this coating step anddrying and degreasing step three times, baking was carried by rapidthermal annealing (RTA) for one minute at 650° C. (baking step). Afterrepeating four times a process of carrying out the coating step anddrying and degreasing step three times followed by a baking step ofbaking the entire layer, baking was carried out by RTA for 10 minutes at650° C. to form a piezoelectric layer 70 having total thickness of 800nm by a total of 12 successive coatings.

Subsequently, after forming a platinum film 100 nm in thickness as thesecond electrode 80 on the piezoelectric layer 70 by a DC sputteringmethod, baking was carried out by RTA for 10 minutes at 650° C. to forma piezoelectric element 300 of a piezoelectric layer 70 of piezoelectricmaterial containing a perovskite compound having the compositional ratio0.75 Bi (Fe_(0.95)Mn_(0.05)) O₃-0.25 BaTiO₃, and 2 mol % SiO₂ withrespect to the perovskite compound.

Second Working Example

A piezoelectric element 300 was formed analogously to the first workingexample, except that the Si compound was not added to the precursorsolution, and the piezoelectric material of the piezoelectric layer 70was composed of the perovskite compound 0.75 Bi(Fe_(0.95)Mn_(0.05))O₃-0.25 BaTiO₃.

Third Working Example

A piezoelectric element 300 was formed analogously to the second workingexample, except that the mixture proportions of the Bi, Fe, Mn, Ba, andTi metal compounds were changed to give a piezoelectric layer 70composed of a piezoelectric material having the perovskite compound 0.80Bi(Fe_(0.95)Mn_(0.05)) O₃-0.20 BaTiO₃.

Fourth Working Example

A piezoelectric element 300 was formed analogously to the second workingexample, except that the mixture proportions of the Bi, Fe, Mn, Ba, andTi metal compounds were changed to give a piezoelectric layer 70composed of a piezoelectric material having the perovskite compound 0.70Bi(Fe_(0.95)Mn_(0.05)) O₃-0.30 BaTiO₃.

First Comparative Example

A piezoelectric element 300 was formed analogously to the first workingexample, except that the mixture proportions of the Bi, Fe, Mn, Ba, Ti,and Si metal compounds were changed to give a piezoelectric layer 70composed of a piezoelectric material having the perovskite compound 0.60Bi(Fe_(0.95)Mn_(0.05)) O₃-0.40 BaTiO₃, and 2 mol % SiO₂ with respect tothe perovskite compound.

Second Comparative Example

A piezoelectric element 300 was formed analogously to the second workingexample, except that iron tris(acetylacetonate) was used in place of theiron octylate.

First Test Example

For each of the piezoelectric elements 300 of the first to fourthworking examples and the first and second comparative examples, using anFCE-1A made by Toyo Corporation and a φ=400 μm electrode pattern, a 3 Vto 60 V triangular wave having frequency of 1 kHz was applied and the P(polarization)−V (voltage) relationship was calculated. The hysteresisloop of the first working example is shown in FIG. 3, the hysteresisloop of the second working example is shown in FIG. 4, the hysteresisloop of the third working example is shown in FIG. 5, the hysteresisloop of the fourth working example is shown in FIG. 6, the hysteresisloop of the first comparative example is shown in FIG. 7, and thehysteresis loop of the second comparative example is shown in FIG. 8. Asshown in FIGS. 3 to 8, the piezoelectric layers of the first to fourthworking examples and of the first and second comparative examples areferroelectrics.

As a result, polarization was greater in the first to fourth workingexamples as compared with the first and second comparative examples. Inthe first working example, a good hysteresis curve was obtained up to 51V. It was therefore demonstrated that the first working example affordsexcellent insulation properties.

Second Test Example

For each of the piezoelectric elements 300 of the first to fourthworking examples and the first and second comparative examples, using animpedance analyzer HP4294A made by Agilent, relative dielectric constantwas measured at between 25° C. and 300° C. under conditions of 1 kHz and141 mV amplitude. Results are shown in FIG. 9. As shown in FIG. 9, thepiezoelectric layer 70 in the first to fourth working examples hadmarkedly higher relative dielectric constant as compared with the firstand second comparative examples, and relative dielectric constant was320 or above. Specifically, as shown in FIG. 9, relative dielectricconstant at 25° C. was 370 for the first working example, 355 for thesecond working example, 325 for the third working example, and 415 forthe fourth working example, versus 205 for the first comparative exampleand 220 for the second comparative example.

Third Test Example

For each of the piezoelectric elements of the first to fourth workingexamples and the first and second comparative examples, using a D8Discover made by Bruker AXS and CuKα rays as the X-ray source, thepowder X-ray diffraction patterns of the piezoelectric layers at roomtemperature were calculated at φ=ψ=0°. Results for the first workingexample are shown in FIG. 10, results for the second working example inFIG. 11, results for the third working example in FIG. 12, results forthe fourth working example in FIG. 13, results for the first comparativeexample in FIG. 14, and results for the second comparative example inFIG. 15. An example of a 2-dimensional sensed image for the firstworking example is shown in FIG. 16.

As a result, in all of the first to fourth working examples and thefirst and second comparative examples, the perovskite structure (ABO₃structure) was observed to form as shown in FIGS. 10 to 15. The peaksattributed to the piezoelectric layer were one attributed to the (100)plane, observed in proximity to 2θ=22.30 to 22.60°, and one attributedto the (110) plane, observed in proximity to 2θ=31.80 to 32.00°. Whenthe degree of orientation of the peak attributed to the (110) plane wascalculated from the area ratio of the peak attributed to the (110) planeto the sum of the peak attributed to the (100) plane and the peakattributed to the (110) plane, the value was 64% in the first workingexample, 77% in the second working example, 68% in the third workingexample, and 73% in the fourth working example. Thus, these values were60% or above for the first to fourth working examples, showing that allof the oriented films were preferentially oriented with the (110) plane.On the other hand, the orientation of the (110) plane in the firstcomparative example was approximately 36%, and the orientation of the(110) plane in the second comparative example using a precursor solutionnot containing iron octylate was approximately 42%, showing that inneither example were the films preferentially oriented with the (110)plane. The peak attributed to the (111) plane observed in proximity to2θ=40° is attributed not to the piezoelectric layer but instead to theplatinum film of the foundation, and by observing the 2-dimensionalsensed image of FIG. 16 in the ψ-2θ direction, it may be appreciatedthat the (111) plane peak of the piezoelectric layer of the firstworking example is extremely small.

From the results of these test examples, it may be appreciated that inthe first to fourth working examples, in which the piezoelectric layeris 3 μm or less in thickness, is preferentially oriented with the (110)plane, and is composed of a piezoelectric material containing aperovskite compound including bismuth manganate ferrate and bariumtitanate, the relative dielectric constant is markedly higher and thepiezoelectric characteristics are better, as compared with the first andsecond comparative examples which are not preferentially oriented withthe (110) plane.

To the second electrodes 80 provided as the individual electrodes of thepiezoelectric element 300 there are connected lead electrodes 90 of gold(Au) for example, which lead out from the proximity of the end on theink supply channel 14 side and extend as far as the intimate adhesionlayer 56.

A protective substrate 30 having a reservoir portion 31 that defines atleast part of a reservoir 100 is joined through the agency of anadhesive 35 over the flow-defining substrate 10 having thesepiezoelectric elements 300 formed thereon, and more specifically overthe first electrode 60, the intimate adhesion layer 56, and the leadelectrodes 90. According to the present working example, this reservoirportion 31 passes through the protective substrate 30 in the thicknessdirection and extends across the width direction of the pressuregeneration chambers 12 to constitute the reservoir 100 whichcommunicates with the communicating portion 13 of the flow-definingsubstrate 10, and serves as the common ink chamber for the pressuregeneration chambers 12 as described previously. Optionally, thecommunicating portion 13 of the flow-defining substrate 10 may bedivided into multiple partitions for the individual pressure generationchambers 12, and only the reservoir portion 31 used as the reservoir.Alternatively, for example, the flow-defining substrate 10 may beprovided with pressure generation chambers 12 only, and a componentinterposed between the flow-defining substrate 10 and the protectivesubstrate 30 (for example, the resilient film 50, the intimate adhesionlayer 56, etc.) may be provided with the ink supply channels 14 forconnecting the reservoir with the pressure generation chambers 12.

An area of the protective substrate 30 facing towards the piezoelectricelements 300 is provided with a piezoelectric element retaining portion32 having space sufficient to not impede movement of the piezoelectricelements 300. While the piezoelectric element retaining portion 32 musthave space sufficient to not impede movement of the piezoelectricelements 300, the space may be sealed, or not sealed.

The protective substrate 30 is preferably made of material with acoefficient of thermal expansion substantially identical to theflow-defining substrate 10, for example, glass, ceramic materials, orthe like. In the present working example, a single-crystal siliconsubstrate of material substantially identical to the flow-definingsubstrate 10 is used.

A passage hole 33 that passes through the protective substrate 30 in thethickness direction is provided in the protective substrate 30. The leadelectrodes 90 which lead out from the piezoelectric elements 300 aredisposed such that an area in proximity to the ends of the electrodeslies exposed within the passage hole 33.

A driver circuit 120 for driving the array of piezoelectric elements 300is fastened over the protective substrate 30. A circuit board, asemiconductor integrated circuit (IC), or the like may be used as thisdriver circuit 120. The driver circuit 120 and the lead electrodes 90are electrically connected via connecting lines 121 of conductive wiressuch as bonding wires.

A compliance substrate 40 composed of a sealing film 41 and a fastenerplate 42 is joined onto the protective substrate 30. Here, the sealingfilm 41 is made of a pliable material with low rigidity, and one face ofthe reservoir portion 31 is sealed by this sealing film 41. The fastenerplate 42 is made of relatively hard material. An area of the fastenerplate 42 facing the reservoir 100 constitutes an opening portion 43where material has been completely removed in the thickness direction,and therefore the one face of the reservoir 100 is sealed by the pliablesealing film 41 exclusively.

According to the inkjet recording head I of the present working example,ink is drawn in through an ink introduction port that is connected toexternal ink supply means, not shown; and after the interior has filledwith ink from the reservoir 100 to the nozzle openings 21, in accordancewith a recording signal from the driver circuit 120, voltage is appliedacross the first electrodes 60 and the second electrodes 80 respectivelycorresponding to the pressure generation chambers 12, to induce theresilient film 50, the intimate adhesion layer 56, the first electrode60, and the piezoelectric layer 70 to experience flexural deformationand thereby elevate the pressure inside the pressure generation chambers12 and expel ink droplets.

Additional Embodiments

While the present invention has been described in terms of certainpreferred working examples, the basic configuration of the invention isnot limited to those discussed above. For example, piezoelectric layersmay be made from piezoelectric materials that additionally contain Ni,Co, Cr, Sc, V or the like, for the purpose of improving piezoelectriccharacteristics.

While the preceding working examples depicted examples using asingle-crystal silicon substrate as the flow-defining substrate 10, noparticular limitation to this is imposed, and optionally, othersemiconductor substrates such as Ge, transparent crystalline substratessuch as SrTiO₃, InSnO₃, ZnO, Al₂O₃, or SiO₂, glass substrates, metalsubstrates such as stainless steel or Ti, SOI substrates, or the likemay be used instead.

Further, while the preceding working examples depicted examples ofpiezoelectric elements 300 formed by sequential stacking of the firstelectrode 60, the piezoelectric layer 70, and the second electrodes 80on the substrate (flow-defining substrate 10), no particular limitationto this is imposed, and the invention may be implemented, for example,in piezoelectric elements of longitudinal oscillating type composed ofalternating stacked layers of piezoelectric material andelectrode-forming material that expand and contract in the axialdirection.

The inkjet recording heads of these working examples constitute part ofa recording head unit provided with ink channels that communicate withan ink cartridge or the like, and are installed in an inkjet recordingdevice. FIG. 17 is a schematic diagram showing an example of such aninkjet recording device.

In the inkjet recording device II shown in FIG. 17, cartridges 2A and 2Bare detachably installed in recording head units 1A and 1B provided asink supply means and furnished with the inkjet recording head I. Acarriage 3 on which these recording head units 1A and 1B are mounted ismovably disposed in the axial direction on a carriage rail 5 that isattached to a device chassis 4. The recording head units 1A and 1Brespectively eject a black ink composition and color ink compositions,for example.

The carriage 3 on which the recording head units 1A and 1B are mountedtravels along the carriage rail 5 through transmission of drive powerfrom a drive motor 6 to the carriage 3 via a number of gears, not shown,and a timing belt 7. The device chassis 4 has a platen 8 which isdisposed along the carriage rail 5, and a recording sheet S of arecording medium such as paper which is supplied by feed rollers, notshown, or the like is advanced while wound around the platen 8.

While the preceding first working example described an inkjet recordinghead by way of an example of a liquid ejection head, the presentinvention is directed generally to all manner of liquid ejectiondevices, and, as shall be apparent, may be implemented in liquidejection heads that eject liquids other than ink. Examples of otherliquid ejection heads are recording heads of various kinds used in imagerecording devices such as printers; color material ejection heads usedin the manufacture of color filters for liquid crystal displays and thelike; electrode material ejection heads used for electrode formation inorganic EL displays, field emission displays (FED), and the like; andbioorganic compound ejection heads used in the manufacture of biochips.

The present invention is not limited to piezoelectric elements mountedon liquid ejection heads typified by inkjet recording heads, and may beimplemented analogously in piezoelectric elements for ultrasoundtransmitters and other ultrasound devices, ultrasound motors, orinfrared sensors, ultrasound sensors, heat sensitive sensors, pressuresensors, pyroelectric sensors, acceleration sensors, gyro sensors, andvarious other types of sensors. Further, the present invention may beimplemented analogously in ferroelectric elements such as ferroelectricmemory, or in micro liquid pumps, thin ceramic capacitors, gateinsulating films, and the like.

General Interpretation of Terms

In understanding the scope of the present invention, the term“comprising” and its derivatives, as used herein, are intended to beopen ended terms that specify the presence of the stated features,elements, components, groups, integers, and/or steps, but do not excludethe presence of other unstated features, elements, components, groups,integers and/or steps. The foregoing also applies to words havingsimilar meanings such as the terms, “including”, “having” and theirderivatives. Also, the terms “part,” “section,” “portion,” “member” or“element” when used in the singular can have the dual meaning of asingle part or a plurality of parts. Finally, terms of degree such as“substantially”, “about” and “approximately” as used herein mean areasonable amount of deviation of the modified term such that the endresult is not significantly changed. For example, these terms can beconstrued as including a deviation of at least ±5% of the modified termif this deviation would not negate the meaning of the word it modifies.

While only selected embodiments have been chosen to illustrate thepresent invention, it will be apparent to those skilled in the art fromthis disclosure that various changes and modifications can be madeherein without departing from the scope of the invention as defined inthe appended claims. Furthermore, the foregoing descriptions of theembodiments according to the present invention are provided forillustration only, and not for the purpose of limiting the invention asdefined by the appended claims and their equivalents.

1. A liquid ejection head comprising: a piezoelectric element having apiezoelectric layer and electrodes, wherein the piezoelectric layer is 3μm or less in thickness, the piezoelectric layer being made of apiezoelectric material including at least bismuth manganate ferrate andbarium titanate, and the piezoelectric layer being preferentiallyoriented with the (110) plane.
 2. The liquid ejection head according toclaim 1, wherein the electrodes include a platinum film oriented withthe (111) plane, and the piezoelectric layer is formed on the platinumfilm.
 3. The liquid ejection head according to claim 1, wherein thepiezoelectric layer is a spontaneously oriented film.
 4. The liquidejection head according to claim 1, wherein the piezoelectric materialfurther includes SiO₂.
 5. The liquid ejection head according to claim 4,wherein the piezoelectric layer contains SiO₂ in an amount of 0.5 mol %or more and 5 mol % or less.
 6. A liquid ejection device comprising theliquid ejection head according to claim 1.